Currently, applications of hard coating materials are wide-ranging, and the hard coating materials are used, for example, for improving surface hardness of automobile parts, containers for cosmetics and the like, sheets, films, optical discs, and flat displays. Examples of characteristics required for the hard coating materials include hardness, abrasion resistance, heat resistance, weather resistance, and adhesion. Typical examples of the hard coat materials include radical polymerizable and UV-curable hard coatings (e.g., refer to Non-patent Document 1), and their constituents are a polymerizable group-containing oligomer, a monomer, a photopolymerization initiator and other additives. The oligomer and the monomer are radically polymerized and thus cross-linked by UV irradiation to yield a film with high hardness. This hard coat material has advantages that the time required to be cured is short to improve the productivity and that a negative type photosensitive material based on a general radical polymerization mechanism can be used to reduce a production cost. However, this hard coating material had a problem that since it contains a large amount of organic components, it has less hardness and abrasion resistance than other hard coating materials and therefore it generates cracks resulting from volume shrinkage due to UV-curing.
A touch panel is one of the principal uses of the hard coating materials. Resistance film type touch panels, which are currently the mainstream, cannot be subjected to a high-temperature treatment since a sensor is mounted on the film of the touch panel. Accordingly, the above-mentioned UV-curable hard coatings, which do not require thermal curing or can attain a cured film by low-temperature curing, have been preferably used (e.g., refer to Patent Document 1). On the other hand, in the case of capacitance type touch panels which receive attention in recent years, it is possible to form a transparent ITO (indium tin oxide) film in which crystallization is sufficiently developed since the ITO film is formed on a glass which can be treated at elevated temperatures. On the other hand, since this touch panel does not have such a layer as to function to mitigate external impact that the resistance film type touch panels have, higher hardness is required for the surface protective film of this touch panel. For this situation, for example, there is disclosed a capacitance type touch panel which uses glass with an ITO film as a substrate and has a protective film composed of inorganic SiO2 or SiNx with high hardness, or a transparent resin (e.g., refer to Patent Document 2). However, inorganic hard coatings have a problem that production cost is high since the inorganic hard coatings are formed by forming a film of SiO2 or SiNx at elevated temperatures by CVD (Chemical Vapor Deposition) or formed by performing a high-temperature treatment close to 300° C. for a long time after coating SOG (spin on glass) and therefore energy consumption increases, and moreover a protective film is processed for the purpose of connecting a circuit and therefore the number of processes increases. Therefore, photosensitive hard coat materials with high hardness, which are superior in abrasion resistance and capable of pattern processing, are required.
On the other hand, as a UV-curable coating composition, a composition including (A) metal oxide colloid sol, (B) a hydrolysis-condensation product of alkoxysilane which at least partially contains a specific organic functional group and has a controlled molecular weight distribution, and (C) a photopolymerization initiator are known (e.g., refer to Patent Document 3). However, these do not have pattern processability and therefore these are not sufficient for being applied as a protective film for a touch panel. Further, a photocurable organopolysiloxane composition, which contains (meth)acryloyloxy group-containing organopolysiloxane and a photosensitizer, is disclosed (e.g., refer to Patent Document 4). However, a developer of such a composition is restricted to an organic solvent and the composition is not suitable for a manufacturing process of a touch panel. Further, there is disclosed a resin composition which includes polysiloxane prepared by hydrolyzing and condensing phenyltrialkoxysilane and dicarboxylic anhydride group-containing alkoxysilane, a compound containing a double bond and/or a triple bond, a photopolymerization initiator, and a solvent (e.g., refer to Patent Document 5). However, the hardness and the abrasion resistance of such a composition were insufficient for applying the composition as a hard coating material.